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Battery Memory Reseting?

02-16-2006, 04:37 PM

Hi all,

Im haveing issues with my ridgid cordless set right now. Im finding that my batterys last only for a few minutes if im lucky useing the sawsall. And im lucky if i can even cut a 2x4 with the circular saw. Is there any way to reset the memory on the batteries? or do i have to replace them?
Thanks in advance.

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I don't quite know if this will solve your problem.check your voltage,for starters.then if you have a good battery that is fully charged,jump it to the battery with the low charge(use 2 pieces of wire with allagator clips on each ends.make sure you are on the same poles + to+)give it about 2 min.then charge your battery.this might bring it back.if not use that warranty and get new ones.

A fishing pole is the best cordless tool!

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jump it to the battery with the low charge(use 2 pieces of wire with alligator clips on each ends.make sure you are on the same poles + to+)give it about 2 min.then charge your battery.this might bring it back.

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No i said use a fully charged battery that was good and jump it to the battery that will not charge up.this will give the ba battery a boost so then maybe the charger can charge the bad battery. i am thinking the bad battery is so low on charge that the charger can not get a charge started on it.it sounds funny but it happens sometimes the charger just cannot charge a battery that is holding a low amount of voltage and it needs aboost so the charger can charge. sometimes i know i donot explain myself well enough for other people to understand. i will work on this.well that is my theory and it has worked for me at work when i get a complaint about a battery not holding a charge very long i jump it and charge it again.

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Hello MT I’m not familiar with the tool you are having trouble with, but from the discussion it sounds like Ni-Cads. I’m a retired electronic technician and use a lot of Ni-Cad batteries. After fighting them for many years, I have come to some understanding of getting along with them. Here are a few ideas

Ni-Cads like to be kept fully charged, kept cool, charged at the 14 hr rate, and not be run all the way down.

The 14 hour charge rate is capacity (ampere-hours or AH) divided by 10, times 1.4. For example, a 4 AH battery should be charged at 0.4A for 14 hours. The extra 4 hours is for the power lost to heat in the charging process (inefficiency). That is, battery charging is only 60% efficient. Charging a battery for extended periods can pop the safety seal, allowing the electrolyte to escape, seriously reducing its capacity. The fast charge batteries found in high power equipment do not prefer a fast charge, they just tolerate it better than standard batteries. This leads to temperature.

Ni-Cads are damaged if the internal temperature goes much above 125 deg F. Think about the heat generated when charging. Even more is generated when discharging at a high rate. If you leave a high power tool in the sun on an 80 degree day, the battery temperature could be at 110. Then when you do a heavy cut, the battery internal temp is going to climb way above 125 deg. If the case of a working battery feels warm to your hand, it is plenty hot inside where the electrolyte meets the separator. The inside of my locked truck here in mild Southern Calif is typically 110 deg even on a cool day. In the summer it has gone over 140! Keeping an inexpensive thermometer in your vehicle can be a real eye opener.

Standard Ni-Cads like to be charged at the 14 hour rate because it strikes a balance between the heat of fast charging and the whisker growth of slow charging (really!). Batteries that are left in the near dead condition or are routinely slow charged grow whiskers of plate material that eventually shorts out the cell. (A battery is a number of cells in series which is wrapped in plastic). Normal charging keeps the whiskers from growing. What Chic did when he jumpered his bad battery with a good one to make it take a charge was to burn away the shorting whisker. I have jumpered mine across a car battery, applying over a hundred amps for a few milliseconds and had them recover. (I wore gloves and safety glasses just in case.) As Tacman mentioned, freezing them can work. Anything that breaks the whisker fixes the problem for a short time. When I worked in the aerospace industry, a co-worker used to throw them on the concrete floor. It is wasted effort though. There are thousands of whiskers growing and the only one destroyed is the one shorting the cell. As soon as another one is long enough the cell is shorted again. By the way, shorting is the most common failure mode.

The other main failure mode is reverse charging. In power tools, you never have just one cell - even flashlights usually have two or more. When one cell is completely discharged, it becomes reverse-charged by the current flowing from the others if the tool is kept in operation. It may take a charge again, depending on conditions. Even if it does, its AH capacity is reduced so that it is reverse-charged even sooner next time. It will be the first cell in the battery to fail and the symptom will be a battery that won’t hold a charge. Continuing to use the tool will just reverse-charge the next weaker cell.

So, for those of you still reading: Keep the tool out of the sun as much as possible, stop using it or change the battery pack when it slows down, and recharge it as soon as possible according to the manufacturers instructions, avoiding fast charging if you have the option. If you only have a fast charger, don't try to fully charge it, shoot for 75%. Ni-Cads lose about 1% of their charge per day, so if it sits for many weeks, top off the charge before using it.

As an aside, the Ni-Cad memory problem is highly over-rated. The only time that occurs is when the battery is discharged to the same partial discharge repeatedly. Think of a walkie-talkie that is used 8 hours a day and has 12 hours worth of battery in it. Every night the battery is recharged and eventually it will develop a memory that resists taking more than 8 hours worth of charge. But, they can often be reconditioned if in not too bad shape.

Most battery failures are caused by a dead or reversed cell. All the above applies to NiMH cells. They are even more temperature sensitive and will not take a slow charge. Their claim to fame is higher capacity for a given size. Lead-acid Gel-cells are a bit more rugged (and a whole lot heavier).

And this just scratched the surface!

Ni-Cads are like women - treat them well and you will have a long, happy relationship.

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Sorry guys, I'm not even sure I know how to spell lithium ion. The problem is that I'm largely self taught. The upside is that self-taught people are motivated to learn the material well. The downside is that they only learn what is necessary to accomplish the job at hand. For instance, I built the computer I'm using 9 years ago but I don't know beans about this forum software. What goes in the "Title" bar at the top of the "Reply to Thread" form.

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I found this thread when searching and know it's a full year old but it seems to fit my problem.

I have 5 Dewalt batteries, 14.4 and 18's that are dead. One 18v is only 2 years old and the "good" XRP version. Just dead! I"ve contacted Dewalt and they say "sorry, 90days on batteries". Gee thanks.

My question is, I can get these apart but how is the best way to test each cell if I can't charge the pack to begin with? I'm thinking I can "maybe" use enough good cells to make up 2 or 3 of my packs. Just hate looking forward to spending a few hundred to replace em all and hate tossing them too if it's just a cell or 2 in each pack.
Buying new replacement cells to rebuild a complete pack is way too expensive, unless someone has a good source on cells. I can get new 14.4's for 35 bucks and 18's for 47 bucks at the swap meet from one tool guy that sells only DeWalt. Not sure where he get's em but he's always there and always cheap.